Introduction: This article deals with classroom assessment situations from a socio-cultural perspective. Some characteristics of classroom assessment are identified and described as they relate to the teachers' pedagogical intervention for the monitoring and improvement of students' self-regulation processes. Method: A qualitative methodological approach was chosen for the analysis of one video-recorded assessment situation. One 6th grade mathematics class (12 year-olds) was observed along several periods during which assessment took place. The analysis was performed with an instrument that allowed us to identify global characteristics of the assessment situation, as well as its different components or sections. Results: Results reveal some specific ways that the teacher helps his students in sessions prior to and immediately after the assessment session. These interventions are oriented toward preparation and then to correcting and returning results, maximing the pedagogical benefit. Conclusion: Our conclusion is that self-regulation is a complex ability to be taught and learned. Thus, it cannot be left to chance. On the contrary, it requires specific didactic design in order to promote and guide the transition from external regulation to independent self-regulation of the learning process. (Contains 1 table, 1 figure and 1 footnote.)